There is a growing trend in the automobile industry to use internally adjustable reflector headlamps. Internally adjustable reflector headlamps include a reflector and bulb socket assembly enclosed within a sealed headlamp housing and lens. The orientation of the reflector within the housing is adjustable to control the direction of the light beam cast by the headlamp. Typically, the adjustable reflector is supported by three ball studs that extend from the rear of the headlamp housing and fit within sockets located in three corners of the reflector. The middle ball stud is secured directly to the headlamp housing to provide a fixed pivot point for the reflector. The other two ball studs are connected to a pair adjuster mechanisms secured to the rear of the headlamp housing. By operating the adjuster mechanisms, these two ball studs can be extended and retracted to control the horizontal and vertical orientation of the reflector. Examples of such adjusters include those disclosed in U.S. Pat. Nos. 5,707,133 and 5,214,971 to Burton et al., U.S. Pat. No. 5,483,426 to Lewis et al., U.S. Pat. No. 4,796,494 to Eckenrode et al., and U.S. Pat. No. 4,703,399 to Van Duyn et al.
Recent changes in the United States National Highway Traffic Safety Administration (NHTSA) standards require that if a horizontal adjuster mechanism is used in connection with an internally adjustable reflector headlamp, it must be either non-readjustable after the proper aim has been achieved or be equipped with a non-recalibratable vehicle headlamp aiming device (VHAD) which is set to zero after the proper aim has been achieved. Previously, recalibration of the VHAD was allowable under the NHTSA standards. As such, vehicle manufacturers must either aim the lamps and provide a non-recalibratable VHAD which is properly zeroed or aim the lamps and provide a mechanism to prevent future readjustment. Examples of adjusters which include VHADs that can be recalibrated are disclosed in U.S. Pat. Nos. 5,622,421 and 5,539,625 to Turley, Jr. et al. and U.S. Pat. No. 5,446,632 to Childs et al. However, because of the change in NHTSA standards, the devices disclosed in the above patents can no longer be used in the manner indicated.
One attempt at a design of a mechanism to prevent readjustment (shown in FIGS. 5A and 5B) employs an undercut cap 400 with an interior rim portion 402 that is a smaller diameter ("undercut") than the diameter of the head 404 on the end of the drive shaft 406. However in order for an adjuster to become truly non-readjustable using a cap, the cap must not be easily removed. To create a difficult to remove undercut cap 400, the engagement between the interior rim portion 402 and the head 404 must be such that the interference is very high. Because of the nature of the undercut engagement in this design, the force required to remove the cap 400 after it has been installed is about the same as the force required to install the cap 400. As such, in order to be effective, the undercut cap 400 would be very difficult to install and thus not efficient to assemble.
Accordingly, a need exists for a horizontal headlamp adjuster that may easily be rendered non-readjustable after the lamp has been properly aimed at the factory, conforms to the new NHTSA standards, is cost effective to assemble, and is easily installed.